1. Field of the Invention
The invention relates to an apparatus for regulating the traveling speed of a motor vehicle, comprising a regulator whose control unit is in operative connection with an element controlling the ratio of the fuel-air mixture fed to the vehicle engine, especially the throttle valve, and has means for deactivating the regulator when the foot brake is applied including a switch turning on the brake or stop light, and is provided with a safety circuit operative to deactivate the regulator in the event the switch turning on the stop light, and thus switching off the regulating device, fails to function.
2. Prior Art
With relation to an automatic speed regulating system, it is already known that when a switch turning on the stop light and also switching off the regulating device fails to function, a blocking circuit is provided that responds to a prespecified speed change and thereupon switches off the regulating device (DE-OS No. 20 06 367). Such safety circuits, however, entail the disadvantage that at the failure of the stop light switch, the regulating device acts at least momentarily against the effect of the brake. This may lead, especially with high-powered vehicles, to dangerous situations. The known disadvantages cannot be eliminated by the provision of particularly closely tolerated switch thresholds, since the regulating device otherwise would be needlessly switched off at small irregularities of the travel speed.